1. Field of the Invention
The present invention relates to a method of manufacturing a ceramic electronic part and, more specifically, the invention relates to a method of manufacturing a ceramic electronic part of a structure having an electrode disposed on the surface of a ceramic element.
2. Description of the Related Art
As shown in FIG. 14, for example, a method generally employed in manufacturing a ceramic electronic part of a structure having external electrodes 52a and 52b at the ends of a ceramic element 51 comprises the steps of applying an electrode paste on the ceramic element, and curing or baking it.
For example, this method, as shown in FIG. 15A, comprises the steps of applying an electrode paste 62 of a prescribed thickness including metal powder such as silver powder as a conductive ingredient on the surface plate 60, dipping one end (end surface) 51a of the ceramic element 51 into the electrode paste 62 as shown in FIG. 15B, raising the ceramic element 51 out of the electrode paste 62 as shown in FIG. 15C, applying the electrode paste 62 on the other end (end surface) 51b of the ceramic element 51 (not shown), and thermosetting or baking the electrode paste to form external electrodes 52a, 52b (FIG. 14).
However, the conventional method described above has recognized disadvantages in that applying the electrode paste 62 of a uniform thickness on the end surface of the ceramic element 51 is difficult, and that horn-like projections (not shown) may be formed on the surface of the external electrodes 52a, 52b (FIG. 14) caused by cobwebbings of the electrode paste 62 generated at the time the ceramic element 51 is raised from the electrode paste 62, and specifically, the bigger the size of the ceramic element is, the more noticeable such tendency would be.
The conventional method described above has further recognized disadvantages in that in order to control the thickness or the configuration of application of an electrode paste, a precise control of the viscosity of the electrode paste and adjustment of speed or the number of times of raising action, which may affect manufacturing capacity, may be required.
In addition, in case of manufacturing electronic parts of the type that leads and/or metal plate terminals to be mounted on a substrate are attached on the external electrode, projections and depressions formed on the surface of the external electrode may affect the stability of connection between them, and thus further precise process control may be required, which may interfere with the improvement of productivity.
Accordingly, it is an object of the present invention to overcome the problems described above and to present a method of manufacturing a ceramic electronic part characterized in that the electrode paste can be applied uniformly onto the ceramic element, and that the ceramic electronic part provided with a film of a uniform thickness required for maintaining its performance and external electrodes having highly precise configuration without any projection or depression on its surface is efficiently manufactured.
In order to achieve the object described above, the present invention discloses a method of manufacturing a ceramic electronic part of a structure having an electrode disposed on the surface of ceramic element, comprising the steps of: rotating a roller having an electronic paste to be applied on the peripheral surface thereof to form a thick film electrode at a prescribed speed; dipping at least a part of a ceramic element into the electrode paste applied on the peripheral surface of the rotating roller; and moving the ceramic element being dipped in the electrode paste relative to and tangentially of the roller in the direction opposite to the rotation of the roller.
Rotating the roller having an electrode paste to be applied on the peripheral surface thereof to form a thick film electrode and moving the ceramic element relative to and tangentially of the roller in the direction opposite to the rotation of the roller with at least a part of the ceramic element being dipped in the electrode paste on the peripheral surface of the roller ensures that the electrode paste of a prescribed thickness is applied onto the surface of the ceramic element.
In other words, according to the method of manufacturing a ceramic electronic part of the present invention, in the step of moving the ceramic element relative to and tangentially of the roller in the direction opposite to the rotation of the roller,
(1) the electrode paste on the peripheral surface of the roller is sheared when the ceramic element comes closest to the roller, and then the electrode paste is transferred onto the ceramic element;
(2) thereafter, the transferring point moves tangentially as the ceramic element moves relative to the roller, so that the electrode paste does not undergo any tensile force during transferring operation and thus the configuration of applied electrode paste is stabilized; and
(3) though a tensile force is exerted on the electrode paste at the time the ceramic element comes off the roller, the electrode paste is torn instantaneously and thus generation of cobwebbings is suppressed because the direction of movement of the ceramic element is opposite to that of the rotation of the roller, or if generated, most of them are taken up by the roller without adversely affecting the configuration of the electrode paste applied on the ceramic element, and consequently, application of an electrode paste of a prescribed thickness without forming projections and depressions on the surface can be achieved.
The method of manufacturing a ceramic electronic part according to the second aspect of the present invention is characterized in that grooves are formed on the peripheral surface of the roller.
By employing a roller having grooves on the peripheral surface thereof, the prescribed thickness of the electrode paste can be held on the peripheral surface of the roller, and a uniform thickness of the electrode paste may be applied quickly on the surface of the ceramic element, and consequently, by thermosetting or baking the electrode paste applied thereon, a ceramic electronic part with high dimensional precision may be manufactured efficiently.
The method according to the third aspect of the present invention is characterized in that the type of grooves formed on the peripheral surface is one of;
(a) a plurality of grooves disposed parallel to the periphery of the roller;
(b) a plurality of grooves disposed parallel to the axis of the roller; and
(c) a plurality of grooves disposed parallel to the periphery of the roller and a plurality of grooves disposed parallel to the axis of the roller formed in a grid pattern.
By employing a roller provided on its peripheral surface with grooves of the type (a), (b), or (c), the electrode paste of a prescribed thickness can be held on the peripheral surface of the roller and a uniform thickness of the electrode paste can be applied on the ceramic element, which makes the present invention effective.
The method of manufacturing a ceramic electronic part according to the fourth aspect of the present invention is characterized in that at least either one of the roller and the ceramic element is moved in the prescribed direction so that the ceramic element moves relative to and tangentially of the roller in the direction opposite to the rotation of the roller.
As a method to move the ceramic element relative to and tangentially of the roller in the direction opposite to the rotation of the roller, either one of the roller and the ceramic element may be moved, or both of the roller and the ceramic element may be moved.
The method of manufacturing a ceramic electronic part according to the fifth aspect of the present invention is characterized in that the relation between the velocity of the movement of the ceramic element relative to and tangentially of the roller in the direction opposite to the rotation of the roller V1 and the peripheral speed of the rotation of the roller V2 satisfies the inequality; V1 less than V2.
When the relation between the velocity of the movement of the ceramic element relative to and tangentially of the roller in the direction opposite to the rotation of the roller V1 and the peripheral speed of the rotation of the roller V2 satisfies the condition of V1 less than V2, the procedures of the present invention such as: shear of the electrode paste on the peripheral surface of the roller; transfer of the electrode paste to the ceramic element as described in (1); an improvement in stability of the configuration of applied electrode paste by the relative movement of the ceramic element without exerting a significant tensile force onto the electrode paste as described in (2), instantaneous tearing-off of the electrode paste at the time the ceramic element comes off the roller, and taking up of the cobwebbings onto the roller as in (3) are achieved without fail, which makes the present invention effective.
The method of manufacturing a ceramic electronic part according to the sixth aspect of the present invention is characterized in that a prescribed clearance is provided between the ceramic element and the peripheral surface of the roller, so that the ceramic element and the peripheral surface of the roller do not come in contact with each other when a prescribed portion of the ceramic element is dipped into the electrode paste applied on the peripheral surface of the roller.
By preventing the ceramic element and the peripheral surface of the roller from coming in contact with each other when a prescribed portion of the ceramic element is dipped into the electrode paste on the peripheral surface of the roller, occurrence of chippings on the ceramic element can be prevented, and thus the degree of effect exerted when chippings are mixed into the electrode paste can be alleviated.